Managing a modern electricity grid is very challenging. Energy consumption is constantly changing, while solar panels and wind turbines have added the element of variable production. Power grids must also be designed for the highest load of the year, even if they operate at partial capacity the rest of the time.

The hottest days of summer are critical for power grids, since buildings are using air conditioning equipment at full capacity. When you add the load of all cooling systems in homes and businesses, the burden on the grid becomes significant. If the power company is not prepared for this, electrical faults and blackouts can be expected at several points.


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The fact that air conditioning is the largest load during summer also creates an opportunity. If building owners focus on improving their AC efficiency, the demand on the power grid can be cut drastically. Homes and businesses save on their power bills, while the burden on the electricity grid is reduced.

Factors That Increase Air Conditioning Expenses

The air conditioning needs of a building are strongly determined by its size and intended purpose, as well as the number of occupants and the local climate. Normally, these factors cannot be changed, which means the air conditioning design must adapt to them.

However, there are other aspects that affect air conditioning costs, and they can be improved during the design process:

  • Building envelope: Insulation, airtightness and energy efficient windows can reduce heat gain in buildings.
  • Equipment efficiency: The nameplate efficiency of air conditioning units influences energy expenses. Small units use the Seasonal Energy Efficiency Ratio (SEER), while larger units use the Integrated Energy Efficiency Ratio (IEER).
  • Temperature controls: The thermostat setting also affects energy consumption. Energy usage may increase by up to 3% for every 1°F the thermostat is reduced, according to the US Department of Energy.

How Air Conditioning Loads Affect the Power Grid

The combined load from thousands of air conditioners has another negative consequence. Utility companies must bring all their generation capacity online, and this includes peaker plants with a high operating cost. Distribution and transmission lines are also carrying a high current, which means more power is being wasted as heat.

To summarize, demand peaks are detrimental for both utilities and their customers:

  • Electricity prices become higher, since the most expensive power plants are online.
  • The grid operates less efficiently: power lines and substations carry a high current, and heat dissipation is increased.
  • Electric companies must constantly invest millions of dollars, so their electric grid capacity keeps up with demand.
  • If demand peaks during summer are higher than expected, blackouts are very likely.

The best opportunity to control peaks in air conditioning demand is found on the consumption side. Measures that reduce the power consumption of air conditioners are the most effective. For example, if 1,000 large buildings can reduce demand by 20 kW each, the total load is reduced by 20 MW.

Reducing the Electricity Consumption of Air Conditioning Systems

airconditioners

Air conditioning efficiency is beneficial for both building owners and electricity companies. Insulation deficiencies and air leaks can be detected with an energy audit, and they can then be corrected to reduce the cooling load. A building that keeps most of the heat outside can be cooled with less energy.

Equipment upgrades and smart controls can further improve AC efficiency, allowing a smaller operating cost per ton of cooling capacity. This is a field-proven approach, and there are also emerging technologies that can enhance air conditioning.

Ice storage is a promising upgrade for chiller plants, since the cooling output can continue even when the compressors are off.

  • The HVAC system can be programmed to make ice with off-peak electricity. 
  • Chillers can be deactivated or ramped down during peak demand hours, while cooling loads are met by melting ice.

A district cooling system of this type has been operating in Chicago since 1995. It serves over 120 buildings, using five chiller plants and four ice storage systems.

Batteries also have promising applications in peak demand reduction. They can be programmed to supply their stored energy precisely when the grid is experiencing a high demand. Battery systems are still held back by their high price, but the outlook is promising. The International Renewable Energy Agency (IRENA) has concluded that energy storage costs could drop by up to 60% by 2030.

 

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